Elimination of power line interference in radio receiving hookups



March 4, 1941. BQLE 2,233,566

ELIMINATION OF POWER LINE INTERFERENCE IN RADIO RECEIVING HOOKUPS FiledNov. 16, 1938 2 Sheets-Sheet l ZZ navy/v5 J 25 22 2 v 0 O E z l4 z 2 J5J9 I 25 26 Q I 2 20 I iii izza 7% BY W March 4; 1941.

ELIMINATION OF POWER LINE INTERFERENCE IN RADIO RECEIVING HOOKUPS FiledNov. 16, I938 2 Sheets-Sheet 2 k W 7 H W BK g N Y! N N I I R m |!I\ w 5w- 4 R R w kfi E v l 2 Q \fl i...

W M) [Q m w ---v R K s) Q 17 Ki Hhh 1 Jimaniar M F. E. BOLE 2,233,566

Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE ELIMINATION OF POWERLINE IN TERFER- ENCE IN RADIO RECEIVING HOOKUPS Application November 16,1938, Serial No. 240,895

11 Claims.

This invention relates to the elimination of power line interference inradio receiving hookups.

Over a period of years numerous attempts have been made to reduce andeliminate electrical interference experienced in the operation of radioreceiving sets. Very little progress has been made in this directionbecause of the fact that the manner in which this trouble is transmittedto the receiving apparatus has not been fully appreciated. I have foundthat the greater proportion of this interference is set up in the powerline of the receiving apparatus, and accordingly it is necessary toprovide means which will eliminate this interference from the powerline.

A difiiculty which exists is the fact that while one given means mayeliminate the interference set up by one cause, it does not eliminateinterference simultaneously set up from other causes.

It is an object of my invention to provide means for eliminating theinterference from the power line of radio receiving apparatus which isso constituted that it can be set to eliminate interference arising fromvarious different sources at the same time.

A still further object of the invention is to provide a simple type ofdevice for the elimination of interference which may be varied in asimple manner to remove the various types of interference from varioussources by a simple process of elimination.

With these and other objects in view, the invention consists in a unitwhich is connected in parallel with the power line and embodies variousdevices employed in a combination or combinations as selected toeliminate the various types of interference experienced at a given time,the unit including a switch member which may be: 40 operated to vary thecombinations employed to suit the device to the conditions obtained at agiven time.

The invention will be fully appreciated by reference to the followingdetailed specification taken in conjunction with the accompanyingdrawings.

In the drawings Figure 1 discloses a wiring diagram of the unitemploying a series of switches in the various lines, selectivelyoperable to connect or disconnect devices suppressing interferencewaves. Figure 2 is a diagrammatic view showing the character of thewaves pro-- duced by one type of interfering electrical apparatus andthe manner in which they are suppressed by a combination of devicesemployed in the unit. Figure 3 is a partly sectional view of a masterswitch control which may be employed to operate the unit. Figure 4 is awiring diagram incorporating a control switch.

Referring to the drawings, Ill indicates one side of the power line andH the opposite side. In View of the fact that in modern power systemsone side of the secondary distribution system is always grounded, it hasbeen assumed for purposes of illustration, that line H is the groundedside of the circuit as is shown in drawings, Fig. l. The unit accordingto the present invention consists of a circuit or circuits connected inparallel with the power line by tapping in or otherwise connecting theleads [2 and I3. These circuits are so arranged as to offer a relativelylow impedance to the current at the interfering frequency while at thesame time preventing any appreciable loss of energy at the powerfrequency. Lead l2 incorporates an inductance coil M which by means ofthe connecting line It), resistance l6 and condenser ll connects lead l2with lead It. Similarly lead I3 is connected through the inductance coilI8 and lead 89 incorporating the resistance 20 and condenser. H to lead12. In the lines I 5 and I9, switches 22 and 23 respectively areincluded so that, as will later be explained, the associated coils,resistances and condensers may be connected in, or taken out of thevarious circuits in such combinations as may prove to be necessary underexisting conditions. The lines l5 and I9 may be connected to the ground24 in a selective manner, such as by the switches 25 and 26 whichconnect either side of the line with the ground lead 21. In the groundlead 27 by passing lines 28 and 29 may be incorporated, line 28employing a switch 30 and line 29 incorporating a switch 3| and acondenser 32.

By means of various switches incorporated in the various lines as abovereferred to, it will be realized that many circuit combinations can beachieved. By way of example let it be assumed that interference is beingset up in one side ID of the power line. Assuming that all the switchesare open, switch 22 is closed so that current at the interferingfrequency is passed through lead l2, inductance Hi, lead l5, resistancel6, and condenser H to the opposite side of the line, during whichpassage the interferingwaves are greatly reduced in strength due toattenuation and, in addition, the circuit acts as a Joy-pass, preventingthe greater part of the interfering current from entering the receivingset. Assume that the interference is caused by an electrically operatedrazor, the interfering waves set up thereby being diagrammaticallyillustrated at A, Figure 2. The by-pass circuit consisting of theinductance coil l4, resistance l6 and condenser H, in series, has theeffect of attenuating the interfering wave and at the same timeby-passing the interfering current, so that less of the inter- 32 mightsufficiently reduce the interfering waves so as to render theminaudible, depending of course upon the type of interference. Thisoperation would increase the capacity in the circuit, due to thegrounding of line I I, and the increased capacity might function tofurther reduce the interfering current to the point where theinterference would be inaudible. In the case where the interference wasarising on both sides of the power line, the closing of the switch 23 inaddi tion to switch 22 would have the effect of passing the waves onside I l of the power line through the inductance [8, lead 13,resistance 20 and condenser 2I, and provide for a somewhat similareffect on that side of the line to that described in the case of sideI0. In this instance switch 26 might be closed to ground line 19 throughswitch 3| and condenser 32. It will also be observed that when switches26 and 3| are closed, condenser 32 will be in parallel with theseriesarrangement of inductance l8 andthe inductance of one side of the powercircuit as mentioned above, thus forming a parallel resonance circuitinstead of increasing the capacity of condenser 2|.

It is pointed out that interference originating on one side of the powercircuit, might be very different from interference coming from theopposite side and this would require different combinations ofinductance, resistance and capacity for the two by-pass circuits. Forinstance, if the circuit required for side Hi, involved the inductancecoil l4, resistance l6, and condenser I! alone, which combination wassufficient to eliminate the interference from that side of the line,then the connection for the other side of the line, that is line H,might require the condenser and ground connection through switches 26and 3|, thus connecting condenser 32 in parallel with inductance l8 andresistance 20 together with the inductance of one side of the powercircuit, as already explained.

It may be found that the combination of the inductance coil l4 andresistance 16 for instance, condenser 32 and ground 24 is all that isrequired in one side of the line to eliminate the interference being setup therein. In such a situation, switch 22 would remain open. In casethe interference was originating on the grounded side of the line, thesame procedure might not necessarily be followed, on account of the factthat the grounding of line H would place condenser 32 in parallel withinductance I8 and resistance 20 when switch 26 was closed. In such acase, switch 23 would be closed in place of switch 26, in order toreproduce conditions similar to those obtaining for line I when switches25 and 3| are closed and switch 22 left open.

It will be appreciated therefore that the unit is of such character thatby closing and opening the several switches employed in each lead, adifferent effect may be obtained on either side of the line, or similareffects may be produced in both sides of the line. Thus, by a process ofelimination through the successive operation of the various switchesreferred to,'interference on both sides of the line may be eliminated.

It will be appreciated that resistances l6 and 20 connected in lines land I9 are employed for the double purpose of dissipating energy fromthe interfering waves and to limit the current fiow in case of abreakdown of any of the condensers in the circuit.

The several switches above referred tomay be operated from a mastercontrol switch employing a sufficient number of contacts as to providefor setting up all the various combinations individually, that is onecombination for each position of the master switch. For instance,referring to Figure 3 the master switch 33 is disclosed which may beconstructed to employ a series of spaced apart axially aligned'annularmembers 34, which are insulated from one another and held rigidly. Thesemembers are provided each with an annular recess 35, on the ledge ofwhich are carried a plurality of stationary contacts 36. Each one ofthese contacts on each member is designed to provide for the closing oropening of a switch in the unit. A rotary disc 31 is provided for eachannular member fitting into the recess overlying the contacts 36, thediscs being rigidly secured to the rotary shaft 38. Each disc carries acontact 39 which is designed to make.

contact with any one of the contacts 36 on the annular member with whicheach disc is associated, so that with each turn of the shaft 38 thecontact on each disc 31 is caused to contact with an axiallyalignedcontact 36 on each an nular member 34. Consequently, assumingthere were six annular members, six contacts are made along the lengthof the master switch, which may effect the closing of the majority ofswitches in the unit, or may effect the closing of but one or more. Inthis connection it will be appreciated that on some of the annularmembers 34 certain of the contact switches will not be connected,-sothat the switch in the unit to which they would ordinarily correspondwould then not be operated when such a contact was made.

The operation through the master switch is more aptly illustrated inFigure 5 where a practical Wiring diagram is illustrated and connectedwith the master switch which is shown diagrammatically, there being fiveannular members 34 with cooperating rotary discs 31, for the sake ofsimplicity. shown in the members 34, and contact 39 on each disc 31 isshown projecting from each disc for the sake of clarity, to make contactwith the contacts 36. In this figure the contacts 39 are all engagingcontact 36 of the members 34. From this it will be noted that the firstelement of the master switch which are numbered l to 5 connectsinductance l8, resistance 20 and condenser 2I across the power linethrough the lead l2 to the side Hi. The second switch element connectsinductance l4, resistance lfiand condenser ll through lead l3 to theopposite side ll of the power line. The action in connection with thesetwo elements is the equivalent of closing switches 22 and 23. ,The thirdelement connects ground 24 in the circuit and therefore func: tions toclose switch 25. The fourth element of However, only four contacts arethe switch also cuts in the ground 24 and therefore functions to closeswitch 26. The fifth element cuts in condenser 32 and ground 24, so ittherefore functions to close switch 3|. As a result, therefore, all theelements in the unit function for the first position of the masterswitch.

On the second position of the master switch only one change takes place,it being clear that in the case of the elements I, 2, 3 and the samemembers of the unit are kept in circuit, whereas in the case of element4 the contact 36 is neutral so that the resistance ground is eliminatedfrom the circuit, which amounts tothe opening of the switch 28. Thus,inductance I8 is coupled across the line through the resistance 20 andcondenser 2| to side It of the line, while inductance I4 not only iscoupled across the line through condenser IT to side II, but is alsoconnected to ground 24, via the condenser 32.

In the case of the third shift, the first element of the master switchdoes not function since the third contact is neutral. In view of thisthe condenser 2I is cut out of the circuit but the remaining elements ofthe switch connect exactly the same members in the unit as in the firstshift, since element 4 of the switch through its third contact 36functions to maintain ground 24 in the combination again. Thus, on. thethird shift switch 23 of the unit is opened and the switch 26 is againclosed. In this arrangement inductance I4, resistance I6 and condenserII are connected across the line, whereas inductance I8 is notconnectedacross the line, but is grounded through switch 26, switch 3|and condenser 32. At the same time inductance I4 resistance It andcondenser I1 is grounded through switch 26, switch 3i and condenser 32.

In the case of the fourth shift, element I of the master switch does notfunction, since the fourth contact is neutral. The same condition existsin element 2. Thus, both switches 22 and 23 are left open, eliminatingthe condensers II and 2| from the combination. However, element 3includes in the combination with inductance I4, the ground 24, whileelement 4 includes the ground 24 with inductance I8. Element 5 cuts inthe condenser 32. Thus, the circuit established connects bothinductances I4 and I8, resistances I 6 and 29 to ground Via thecondenser 32.

According to the wiring of the unit as shown, 31 combinations may bemade so that 31 contacts would occur around each element 34. Thus,

' by continuing the rotation of the master switch through the various 31positions, and having regard to the fact that the contacts may beneutral or connected, as is clear from the above illustration, whereinthe master switch was rotated through four contacts, it will beappreciated that all the combinations it is desired to set up may be setup through one complete rotation of the master switch, stopping at eachcontact point through the complete rotation.

If desired, the positions of the master switch may be numbered orlettered, and having regard to the position to which the master switchmay be rotated the operator can readily determine what combination isbeing employed for the immediate setting of the switch. It is thereforea very simple matter to set into operation whatever combination isrequired by selecting the position at which the switch should be set.Moreover, it is a very simple matter when interference is encountered torotate the switch through its: successive positions and by a process ofelimination set up those combinations which will eliminate the trouble.It is obvious, of course, that such a construction might be employed asa testing apparatus which might determine the cause of interference,having regard to the combination used to eliminate it, and the operatorof the receiving apparatus furnished with an interference eliminatingdevice which employs those combinations alone. In other words, it wouldbe possible to manufacture units employing only one or a few of thecombinations involved in the unit described, which would be employed toeliminate certain known causes of interference. This would obviate thenecessity of a more expensive unit employing all the combinations, someof which would not be necessary in instances of this character.

In the case of some proposals in the past for eliminating interference,a measure of success has been achieved in eliminating noise caused byinterference, the source of which is closely adjacent to the receivingapparatus. An important advance is made in the present development byreason of the fact that the unit will operate to eliminate interference,whether the device causing the interference is close to the receiver orlocated at any distance away. and having any effect on the receiver.

Various modifications may be made in this invention without departingfrom the spirit thereof or the scope of the claims, and therefore theexact forms shown are to be taken as illustrative only and not in alimiting sense, and it is desired that only such limitations shall beplaced thereon as are disclosed in the prior art or are set forth in theaccompanying claims.

I claim:

1. Apparatus for eliminating the transmission of power line interferenceto radio receiving sets comprising, in combination, a pair of parallelpaths connected across said power line, each path including aninductance element, a resistance element, and a condenser connected inseries, a third condenser having a connection from one terminal thereofto ground, and switching means for connecting the ungrounded terminal ofsaid third condenser selectively to points on said parallel pathsintermediate two of the elements in each path.

2. Apparatus for eliminating the transmission of power line interferenceto radio receiving sets comprising, in combination, a pair of parallelpaths connected across said power line, each path including aninductance element and a condenser connected in series, the condensersin said paths being connected adjacent opposite sides of said line, athird condenser having a connection from one terminal thereof to ground,and switching means for connecting the ungrounded terminal of said thirdcondenser selectively to intermediate points on said parallel paths.

3. Apparatus for eliminating the transmission of power line interferenceto radio receiving sets comprising, in combination, a pair of parallelpaths connected across said power line, each path including aninductance element, a resistancei element, and a condenser connected inseries, the condensers in said paths being connected adjacent oppositesides of said line, a third condenser having a connection from oneterminal thereof to ground, and switching means for connecting theungrounded terminal of said third condenser selectively to points onsaid parallel paths, said points being intermediate the in questionmight be condenser and the adjacent element in either of said parallelpaths.

4. Apparatus for eliminating the transmission of power line interferenceto radio receiving sets comprising, in combination, a pair of circuitpaths connected adjacent opposite sides of said line, and switchingmeans for selectively completing and interrupting a bridging connectionfrom a point in one of said paths intermediate two of the elementsthereof to a point in the other of said paths intermediate two of theelements thereof.

5. Apparatus according to claim 4 and including a third condenser havinga connection from one terminal thereof to ground, and switching meansfor connecting and disconnecting the ungrounded terminal of said thirdcondenser to said bridging connection.

6. Apparatus for eliminating the transmission of power line interferenceto radio receiving sets comprising, in combination, a pair of circuitpaths, each including an inductance element, a resistance element, and acondenser connected in series, switching means for selectivelyconnecting and disconnecting said paths across said power line with thecondenser elements of said paths connected adjacent opposite sides ofsaid line, a third condenser having a connection from one terminalthereof to ground, and switching means for connecting the ungroundedterminal of said condenser selectively to points on said pathsintermediate two of the elements in each path.

7. Apparatus for eliminating the transmission of power line interferenceto radio receiving sets comprising, in combination, a condenser, aswitch for connecting said condenser to one side of said line, aresistance element and an inductance element connected in series withsaid condenser to the opposite side of said line, a second condenser anda second switch element for connecting the second condenser to theopposite side of the line, a second resistance element and a secondinductance element connected in series with said second condenser tosaid one side of said line, a grounded circuit path including acondenser and a third switch element connected in series, and a pair ofadditional switch elements connecting the free end of said groundedcircuit path respectively to intermediate points on the circuit paths ofsaid first and second condensers.

8. Apparatus for eliminating the transmission of power line interferenceto radio receiving sets comprising, in combination, a condenser, aswitch for connecting said condenser to one side of said line, aresistance element and an inductance element connected in series withsaid condenser to the opposite side of said line, a second condenser anda second switch element for connecting the second condenser to theopposite side of the line, a second resistance element and a secondinductance element connected in series with said second condenser tosaid one side of said line, a third condenser having one terminalthereof connected to ground, and two additional switch elements forconnecting the ungrounded terminal of said third condenser selectivelyto points on the circuit paths of said first and second condensers, saidpoints being intermediate two of the elements in each path,

v9. Apparatus according to claim 7 wherein said switch elements areformed. as rotar; switch elements, each having a plurality of positionsfor closing or opening the switch element, and including a commoncontrol element for simultaneously operating the rotary parts of saidswitch elements, whereby different circuit combinations are establishedin different positions.

of said common control element. v

10. Apparatus according to claim 8 wherein said switch elements are eachprovided with a movable part having a plurality of positions for closingor opening the switch element, and including a common control elementfor simultaneously operating the movable parts of said switch elements,whereby different circuit combinations are established in differentpositions of said control element.

11. Interference eliminating means for wireless receivers comprising a,pair of adjustable filters connected across the supply lines for saidreceiver, each filter consisting of an inductance, a capacity and aresistance connected in series,

the order of the elements being reversed in each filter whereby the paththrough the filters from each line will lead through the inductance inone filter and through the capacity in the other, switches in each ofthe filters between the capacity and the line, a grounded capacity,switches adapted to connect the grounded capacity in series or inparallel across each filter and a master controller for operating saidswitches and adapted when operated to form a succession of alternativeconnections varying the inductance and capacity of the filters.

FLOYD EDWIN BOLE.

